Reversing rheostat



Patented Nov. 11', 1952 UNITED STATES PATENT OFFICE 2,617,911 REvER's'ING RHEos'TAT Richard A. Carey and Maurice N. Dooley, Montclair, N. J. Application May 29, 1951, serial No. '228,836

(o1. coi-4s) 2 Claims. 1

This invention relates to a rheostat and in particular to a reversing type for use in vcontrolling electric motors, particularly small electric motors, such as those which are used in the driving of model railroads.

In specialized applications where model study is involved, the performance demands of a device frequently are such thatit must b'e provided with a high degree of llexibility as well as structural features which peculiarly t it to the purpose in View.

The resistance of the rheostat and its power handling capabilities or safe vdissipating rating may be of any value or values that are considered necessary or desirable. The following are among the several novel features that make the inven'- tion particularly adaptable to be used for 'con'- trolling a model railroad.k No reversing switch is needed. A control handle instead of a knob is used. The handle more nearly looks and functions like a throttle in a prototype locomotive. The design is such that the mounting A*distance between any two rheostats can` be kept to a minimum, thus more rheostats will mount on a given panel. The control handle moves through an arc of approximately 90 instead of 300 as with the conventional circular rheostat. The position of the control handle indicates the direction of the train. Only four connections are needed: two to the power source and two to the rails. A circular rheostat and reversing switch require ten connections to be made.

Thus, for example, in model railroading one of the requirements for a control rheostat is that it be subject to adjustment readily and that it also have an appearance which will make it essentially a prototype of a full scale apparatus.

The instant invention provides a reversing rheostat useful for the control of motors driving model railroads which rheostat is readily connected into the circuit and incorporated into a control panel in a manner which will render it essentially a prototype of a full scale control unit and which will make it operatively useful to reverse and control the electric current supply to the apparatus. The invention also provides a compact rheostat structure which lends itself to incorporation into an electric circuit for control of the railroad by means of a few simple connections readily understood.

The invention further preferably provides a unitary structure in a casing with electrical connections made readily for incorporation into an electric circuit.

Other objects and advantages of the invention will in part be obvious and in part will appearI hereinafter.

The invention thus is embodied in a reversing rheostat structure which is characterized by being formed essentially as a unitary casing carrying a pair of double rheostats mounted on the body thereof, wiping contact being made with these rheostats by a pivotally mounted bifurcated conductor carried by a handle forming a prototype of an engine throttle, which structure is adapted to be incorporated into a control panel for a model railroad, the whole being lcharacterized by the features of construction, com'- bination of elements and arrangements of parts hereinafter set forth in greater detail. The invention can be more readily understood by reference to the drawings accompanying the instant specification in which Fig. 1 is a perspective View of one embodiment of the invention;

Fig. 2 is a similar perspective view of another embodiment of the apparatus having one of the rheostat structures cut away and part of the apparatus in section to show the unitary arrangement of parts;

Fig. 3 is an embodiment showing a diiferent arrangement of wiping contacts, with portions broken away to show internal construction;

Fig. 4 is a simple schematic electrical diagram of the device showing the manner in which it can be connected into -a control circuit or a model railroad; and

Fig. 5 is a cross section of the upper portion of Fig. 2.

Referring to Fig. l, 10 represents the body of the instrument, which may be molded of plastic. As shown in Fig. v2, the body or frame may be formed of a sheet metal element -stamped in the appropriate projected shape and bent to form a boxlike arrangement; II and I2 are double rheostats each of which comprises an insulating core on which are wound two separate sets of turns terminating in the contact terminals I3, I4, I5 and I 6. The preferred embodiment of the structure for reasons of safety calls for having the coils themselves covered with a ceramic insulating material designated in Fig. 2 as II. Electrical contact with the coils is made within the structure in Figs. 1 and 2 by a yoke comprising a forked or bifurcated pair of wiping arms I8 and I 9 which are mounted at 2D on the pivotally mounted lever 2| which is pivoted at point 22. At pivot point 22, electrically connected respectively through the frame or body I0 are a pair of electrical lugs 24 which provide electrical contact 3 through the extension of the wiping arms I8 and I9 at the pivot point. Lever 2l itself is made of insulating material such as plastic or phenol formaldehyde resin or hard rubber. The entire body may similarly be made of insulating material corresponding to that of the handle, and one form of this structure comprises a phenol formaldehyde resin which is cast in a rubber mold with a setting catalyst adapted to cause the resin to set when it is heated for an hour at about 175 F.

In Fig. 2 enough of the structure has been cut away to show the manner in which the contacts I8 and I9 wipe the inside surface of the resistance coils mounted on the frame and also to show the manner in which electrical contacts are carried up from the coils of the pivot point of the lever 2l. Fig. 2 also shows how a metal frame may be pre-formed and bent to provide extending members holding the ends of the coil frames and the pivot structure.

In Fig. 3 there is shown a View of a different embodiment of the apparatus in which the parts are similarly identied. The essential difference in arrangement calls for having the wiping contacts run on the outside `of the two electrical coils, thereby forming an essentially Y-shaped yoke. The ceramic coils can be brought substantially into contact Within the frame, being placed on the insulation for electrical separation of the parts and the wiping contacts maintained in spaced relationship by being made to run on the outside of the electrical coils. In both embodiments the reverse electrical connection is made by carrying a wire 25 crossing from points I3 to l5, which are diagonally opposite geometrically and electrically, and similarly carrying a wire 26 from point I4 to point I6.

These electrical connections are better understood by reference to Fig. 4 which is the schematic electrical diagram of the apparatus wherein the electrical parts have been numbered .with designations corresponding to those used in Figs. l, 2 and 3. The schematic indication of the connection of the rheostat to a power supply and to the track on which the model train will run is also shown in the diagram.

As may be seen in Fig. 1, the slot 30 in the top of the frame permits the upper end of the drive handle to travel to the desired or required distance, depending on the direction and speed desired of the motor 34. The slot is designed to act as a stop for the lever handle, thereby eliminating the necessity for physical stops to be provided at the contact arms. The contact arms are provided with wiping brushes 3l which are maintained in contact with the coils by the spring action of the wiping arms, which are preferably made of relatively rigid sheet metal, as shown in Fig. 5. Pivot point 22 may be established by a pair of cooperating screws 33, which hold the lever 2l with respect to the frame Il), and which 4 also hold the connection lugs 24 in place, as well as providing an upper pivot point for the contact arms and maintaining them in fixed relation to the lever 2l as it is moved back and forth. The coils are spaced at a predetermined relationship between the coil forms by the U-shaped end members 32, which may take the form of sheet-metal pieces bent at each end to provide holding lugs for the coil forms by tting into slots formed in the ceramic or other insulating material of the coil forms at the ends thereof. These slots are indicated in dotted lines in Figs. 2 and 3.

Though the invention has been described with only a limited number of embodiments, it will be understood that variations thereof may be made without departing from the spirit or scope of the invention by those skilled in the art and accordingly the invention is defined in the accompanying claims.

What is claimed is:

1. A reversing rheostat comprising two pairs of resistance elements, said elements being cross-connected, a frame holding said resistance elements in fixed spaced relation to each other, a yoke mounted on said frame oriented between said resistance elements, said yoke carrying a pair of contact brushes, said yoke being pivotally mounted in said frame, each of said brushes making sliding Contact with correspondingly placed resistors, variation in placement of the contacts being determined by the angular pivoting of the yoke about its pivot point.

2. A reversing rheostat comprising two pairs of cross-connected resistance elements mounted on insulating cores, each having an externally protective insulating covering, said resistance elements being held in fixed spaced relationship wherein contact is made with said elements in the space therebetween, a frame carrying said resist-ance elements, a pivot on said frame, a yoke pivoted at said pivot carrying electrical contacts meeting said coils, said yoke being angularly displaceable about its pivot point to vary the point of contact with said resistance elements all points between the extremes of the position of the yoke being in electrical contact with the rheostat.

RICHARD A. CAREY. MAURICE N. DOOLEY.

REFERENCES CITEB The following references are of record in the file of this patent:

UNITED STATES PATENTS 

